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See detailA metagenomic approach from aphid’s hemolymph sheds light on the potential roles of co-existing endosymbionts
De Clerck, Caroline ULg; Fujiwara, Akiko; Joncour, Pauline et al

in Microbiome (2015), 3(63),

Background: Aphids are known to live in symbiosis with specific bacteria, called endosymbionts which can be classified as obligate or accessory. Buchnera aphidicola is generally the only obligatory ... [more ▼]

Background: Aphids are known to live in symbiosis with specific bacteria, called endosymbionts which can be classified as obligate or accessory. Buchnera aphidicola is generally the only obligatory symbiont present in aphids, supplying essential nutrients that are missing in the plants phloem to its host. Pentalonia nigronervosa is the main vector of the banana bunchy top virus, one of the most damageable viruses in banana. This aphid is carrying two symbionts: B. aphidicola (BPn) and Wolbachia sp. (wPn). The high occurrence of Wolbachia in the banana aphid raises questions about the role it plays in this insect. The goal of this study was to go further in the understanding of the role played by the two symbionts in P. nigronervosa. To do so, microinjection tests were made to see the effect of wPn elimination on the host, and then, high-throughput sequencing of the haemolymph was used to analyze the gene content of the symbionts. Results: We observed that the elimination of wPn systematically led to the death of aphids, suggesting that the bacterium could play a mutualistic role. In addition, we identify and annotate 587 and 250 genes for wPn and BPn, respectively, through high-throughput sequencing. Analysis of these genes suggests that the two bacteria are working together for the production of several essential nutrients. The most striking cases are for lysin and riboflavin which are usually provided by B. aphidicola alone to the host. In the banana aphid, the genes involved in the production pathways of these metabolites are shared between the two bacteria making them both essential for the survival of the aphid host. Conclusions: Our results suggest that a co-obligatory symbiosis between B. aphidicola and Wolbachia occurs in the banana aphid, the two bacteria acting together to supply essential nutrients to the host. This is, to our knowledge, the first time Wolbachia is reported to play an essential role in aphids. [less ▲]

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See detailIdentification of the bacterial symbionts of the banana aphid Pentalonia nigronervosa and characterization of their roles
De Clerck, Caroline ULg

Doctoral thesis (2015)

Les insectes sont caractérisés par une incroyable capacité d’adaptation à de nombreux environnements et modes d’alimentation, qui est liée au fait que la majorité des insectes (voire tous) hébergent des ... [more ▼]

Les insectes sont caractérisés par une incroyable capacité d’adaptation à de nombreux environnements et modes d’alimentation, qui est liée au fait que la majorité des insectes (voire tous) hébergent des symbiontes intra ou extracellulaires. Ces associations symbiotiques sont très diverses et peuvent aller d’un mutualisme obligatoire à un parasitisme facultatif. Les pucerons, en particulier, sont connus pour vivre en symbiose avec au moins une bactérie obligatoire qui leur fournit les nutriments essentiels absents du phloème dont ils se nourrissent : Buchnera aphidicola. La plupart des symbiontes d’insectes étant incultivables, les technologies moléculaires modernes se sont avérées des outils puissants dans la compréhension des interactions hôte-microorganisme et la caractérisation du rôle joués par ces symbiontes. Les études génomiques ont mené à la découverte des plus petits génomes bactériens jamais observés, et ont permis une étude plus poussée des symbiontes secondaires et de leur évolution. Pentalonia nigronervosa, le puceron noir du bananier, lest le vecteur principal du virus des sommets touffus du bananier, l’un des virus les plus dommageables en culture bananière. Très peu d’études sont néanmoins disponibles sur ce vecteur et rien n’était connu sur la population symbiotique hébergée par cet insecte jusqu’à cette étude. Dans cette thèse, nous avons découvert que le puceron du bananier contient deux symbiontes : B. aphidicola (BPn) et Wolbachia sp. (wPn); et cela dans tous les pucerons testés, quelle que soit leur origine géographique. La présence de Buchnera était attendue (99,9% de toutes les espèces de pucerons contiennent ce symbionte), mais la détection systématique de Wolbachia nous fait nous interroger sur le rôle que cette bactérie pourrait jouer pour l’insecte hôte, ainsi que sur la raison de sa présence. Wolbachia n’est en effet que rarement détectée chez les pucerons et est surtout connue pour être un parasite qui manipule le système reproducteur de ces hôtes. Malgré tout, des études ont montré que cette bactérie pouvait agir comme mutualiste pour certains insectes, ce qui pourrait expliquer sa présence dans le puceron du bananier. Le second objectif de cette étude a donc été de mieux comprendre le rôle joué par les deux symbiontes de P. nigronervosa. Pour ce faire, différentes techniques complémentaires ont été utilisées. La microinjection d’antibiotiques a été utilisée afin d’éliminer sélectivement wPn et de voir l’effet de cette élimination sur l’hôte. Nous avons observé que l’élimination de wPn donnait systématiquement lieu à la mort du puceron. Un séquençage haut débit de l’hémolymphe (contenant des bacteriocytes) d’un puceron a été réalisé et nous a permis d’identifier et d’annoter 587 et 250 gènes pour wPn et BPn respectivement. L’analyse de ces gènes nous permet d’émettre l’hypothèse que les deux bactéries collaborent pour la production de plusieurs nutriments essentiels pour l’hôte. La situation est surtout frappante dans le cas de la lysine et de la riboflavine, qui sont habituellement produits uniquement par Buchnera chez les autres espèces de pucerons. Dans le cas du puceron du bananier, les gènes impliqués dans les voies de production de ces métabolites sont répartis entre les génomes des deux bactéries, les rendant ainsi toutes les deux essentielles à la survie du puceron hôte. Enfin, une localisation par fluorescence in situ des deux symbiontes a montré qu’ils étaient tous deux localisés dans les bacteriocytes, rendant les échanges de précurseurs et métabolites possibles. En conclusion, nos résultats suggèrent que le puceron du bananier héberge une co-symbiose obligatoire entre B. aphidicola et Wolbachia, les deux bactéries agissant de concert dans l’approvisionnement de l’hôte en nutriments essentiels. [less ▲]

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See detailStudy of essential oil activity on Curvularia sp. a rice leaf spot pathogen in Madagascar
Mamiharisoa Razanakoto, Léa ULg; Parisi, Olivier ULg; Massart, Sébastien ULg et al

Poster (2015, May 19)

Rice leaf spot have been observed on many fields during survey of rice diseases in three regions in Madagascar. Curvularia sp. was the most frequently isolated pathogen from the most severe diseased ... [more ▼]

Rice leaf spot have been observed on many fields during survey of rice diseases in three regions in Madagascar. Curvularia sp. was the most frequently isolated pathogen from the most severe diseased samples. This pathogen has been reported worldwide to cause important losses. Then in this work, we study the possibility to develop an alternative method to control Curvularia sp. Plants or plant extracts have been traditionally used to control human and plant diseases. Nowadays, the problem of residues of phytopharmaceutical products, reinforce the need for research on the development of natural plant extracts to control plant diseases. Madagascar has many endemic plants of interest. The antimicrobial properties of essential oils from Malagasy aromatic plants were evaluated. The main steps of this study are (i) the in-vitro screening of 39 Malagasy essential oils to control this pathogen, (ii) the evaluation of the phytotoxicity (on rice plants) of the efficient essential oils and (iii) the in vivo test of the activity of these non phytotoxic essential oils on Curvularia sp. on rice seedlings. The activity of essentials oils on Curvularia sp. has been tested in vitro during a microscale ELISA plate bioassay using optical density for a rapid evaluation of the biofungicidal activity of the extracts. Essential oils that showed interesting antifungal effect on this pathogen were tested for their phytotoxicity on rice plants. Briefly, one to two drop(s) of essential oils were applied on 3 leaves leaves of three weeks rice seedling. Six essential oils over the 39 tested showed an interesting antifungal activity with a percentage of growth inhibition greater than 70%. Three essential oils tested were phytotoxic as they induced necrotic spots on rice leaves after 48 h. Among three essential oils left, one of them showed an important effect when applied on rice seedling inoculated with a conidial suspension of Curvularia sp. These results confirmed that some essential oils present an antifungal activity. And even some of them are phytotoxic on rice plants, some essential oils show interesting potential to be an alternative method against rice diseases. [less ▲]

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See detailTechnical guidelines for the safe movement of Musa germplasm
Thomas, John; Sharman, Murray; Lassois, Ludivine ULg et al

in Thomas, John (Ed.) Technical guidelines for the safe movement of Musa germplasm (2015)

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See detailVirus indexing and sanitation of international banana collection: insights from a 5-years collaborative effort
De Clerck, Caroline ULg; Parmenter, Kathleen; Vandenhouwe, Ines et al

Conference (2015)

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See detailVolatile organic compounds emitted by Cavendish and Plantain banana plants
De Clerck, Caroline ULg; Kherkhofs, Celine; Berhal, Chadi et al

Poster (2015)

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See detailOccurence of Satellite RNAs associated with Cucumber mosaic virus isolated from banana (Musa sp.) in Ivory Coast
Kouadio, Kouakou Théodore; De Clerck, Caroline ULg; Agneroh, TA et al

in British Society for Plant Pathology - New Disease Reports (2014), 30

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See detailVirus indexing and sanitation of international banana collection: insights from a 5-year collaborative effort
De Clerck, Caroline ULg; Parmenter, Kathleen; Vandenhouwe, Ines et al

Conference (2014, August 14)

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See detailHigh throughput sequencing of aphid haemolymph reveals endosymbiont diversity
De Clerck, Caroline ULg; Leonard, Simon; Joncour, Pauline et al

Conference (2014, May 20)

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See detailExploring the role of symbionts in the banana aphid using high throughput sequencing
De Clerck, Caroline ULg; Joncour, Pauline; Leonard, Simon et al

Conference (2014, April 03)

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See detailSreening of essential oils against rice pathogens isolated from Madagascar
Mamiharisoa Razanakoto, Léa ULg; De Clerck, Caroline ULg; Massart, Sébastien ULg et al

Poster (2014, February 07)

Four predominant isolated pathogens have been identified during survey of rice diseases in three regions in Madagascar. These pathogens were the bacteria Xanthomonas oryzae pv. oryzae and Pseudomonas ... [more ▼]

Four predominant isolated pathogens have been identified during survey of rice diseases in three regions in Madagascar. These pathogens were the bacteria Xanthomonas oryzae pv. oryzae and Pseudomonas fuscovaginae and the fungi Alternaria sp. and Curvularia lunata. These pathogens are causing significant yield reduction on rice, which is the staple food in this country. After the identification of those pathogens, the objective of this work was to identify appropriate control measures against them. Plants extracts has been traditionally used to control diseases in other plant species. Nowadays, the problem of residues of phytopharmaceutical product, reinforce the need for research on the development of natural plant extracts to control plant diseases. Madagascar has many endemic plant of interest and we have evaluated the antimicrobial properties of essential oils from Malagasy plants. The main object of this study is the in-vitro screening of essential oils to control the pathogens isolated on rice in Madagascar. Thirty nine essentials oils from Madagascar had been tested. Activity of essentials oils on Pseudomonas fuscovaginae, Alternaria sp. and Curvularia lunata had been tested using broth media and on agar medium for Xanthomonas oryzae pv. oryzae. The growth of the pathogen (bacteria and conidia) in the presence of the essential oil was evaluated and compared to a control. Nine of the 39 essentials oils showed interesting antimicrobial activity with an efficiency more than 70% against at least one bacterial pathogen. One essential oil inhibited the growth of the two pathogens tested. For fungal pathogens, three essential oils presented an efficiency of more than 70% against at least one fungal pathogen. These results confirm that some essential oils present an interesting antimicrobial activity. The in-situ confirmation on plant of this activity is currently ongoing. [less ▲]

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See detailCombination of Genomic and Proteomic Approaches to Characterize the Symbiotic Population of the Banana Aphid (Hemiptera: Aphididae)
De Clerck, Caroline ULg; Tsuchida, Tsutomu; Massart, Sébastien ULg et al

in Environmental Entomology (2014)

Aphids are known to live in symbiosis with speciÞc bacteria called endosymbionts that have positive or negative impacts on their hosts. In this study, six banana aphid (Pentalonia nigronervosa Coquerel ... [more ▼]

Aphids are known to live in symbiosis with speciÞc bacteria called endosymbionts that have positive or negative impacts on their hosts. In this study, six banana aphid (Pentalonia nigronervosa Coquerel) strains from various geographical origins (Gabon, Madagascar, and Burundi) were screened to determine their symbiotic content, using complementary genomic (16S rDNA sequencing and speciÞc polymerase chain reaction) and proteomic (two-dimensional difference gel electrophoresis coupled with protein identiÞcation by matrix assisted laser desorption-ionization time-of-ßight mass spectrometry) approaches. Despite the geographical heterogeneity, the combined methods allowed us to identify the same two symbionts in the six aphids strains tested: Buchnera aphidicola and Wolbachia. Although B. aphidicola is found in almost all aphid species, the systematic presence of Wolbachia in banana aphids is particularly interesting, as this bacterium usually has a low prevalence in aphid species. Phylogenetic analyses showed that the Wolbachia sp. strain found in P. nigronervosa was very similar to the strain present in aphids of the genus Cinara, known to have developed a strong and long-term symbiotic association with Wolbachia. The high level of asexual reproduction in P. nigronervosa could be linked to the presence of Wolbachia, but its prevalence also suggests that this symbiotic bacterium could play a more essential role in its aphid host. [less ▲]

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See detailINCIDENCE DES MALADIES BACTERIENNES ET FONGIQUES DU RIZ A MADAGASCAR
Mamiharisoa Razanakoto, Léa ULg; De Clerck, Caroline ULg; Massart, Sébastien ULg et al

Poster (2013, December)

Le riz, c’est à la fois la culture la plus cultivée à Madagascar mais aussi la principale base de l’alimentation des malgaches. Même si le pays est à vocation agricole, l’autosuffisance alimentaire n’a ... [more ▼]

Le riz, c’est à la fois la culture la plus cultivée à Madagascar mais aussi la principale base de l’alimentation des malgaches. Même si le pays est à vocation agricole, l’autosuffisance alimentaire n’a jamais été atteinte, et l’importation de riz est toujours importante chaque année. Pour le riz, les maladies constituent le facteur entraînant la mauvaise qualité et la réduction des récoltes. C’est la raison qui nous amène à réaliser le suivi de la maladie de riz présent à Madagascar. L’incidence de la maladie a été évalué par l’observation visuelle des symptômes au champ et l’identité des pathogènes a été confirmée par les tests au laboratoire. Pour cela un échantillonnage a été réalisé dans les régions de Vakinankaratra, Analamanga et Atsinanana. Une enquête a été réalisée durant l’échantillonnage pour récolter les informations qui peuvent nous aider à l’identification de l’agent pathogène. L’isolement a été réalisé en utilisant les milieux standards pour bactéries et pour champignons. Les isolats ont été ensuite identifiés par l’observation des colonies sur boite de Pétri, par des observations microscopique des cellules en présence de différents colorants. Elles ont ensuite été identifiées par analyse moléculaire par séquençage.Dans les régions du haut plateau : les symptômes trouvés sont très variés et l’incidence de chaque symptôme est faible sauf le flétrissement des feuilles de riz. Dans la région Atsinanana, les symptômes trouvés ne varient pas et l’incidence est proche de 100 %. L’isolement des microorganismes à partir d’échantillons de chacune de ces régions confirme les résultats obtenus : Xanthomonas oryzae pv. oryzae correspondait à l’espèce pathogène dominante pour les hauts plateaux tandis que Curvularia lunata correspondait à l’espèce pathogène dominante pourAtsinanana. Ces différences trouvent probablement leur origine dans les conditions climatiques et le mode de culture très différentes entre cette région côtière et les hauts plateaux. [less ▲]

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See detailFirst report of banana mild mosaic virus infecting plantain in Ivory Coast
Kouadio, Kouakou Théodore ULg; Agneroh, Thérèse Atcham; De Clerck, Caroline ULg et al

in Plant Disease (2013), 97(5), 693

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See detailSURVEY OF RICE DISEASES IN THREE REGIONS IN MADAGASCAR
Mamiharisoa Razanakoto, Léa ULg; De Clerck, Caroline ULg; Zalmine, Francia et al

Poster (2013, February 08)

Rice (Oryza sativa) is the most cultivated crop and the staple food in Madagascar. However, the country has never achieved food self-sufficiency and continues to import rice abroad. Rice diseases are one ... [more ▼]

Rice (Oryza sativa) is the most cultivated crop and the staple food in Madagascar. However, the country has never achieved food self-sufficiency and continues to import rice abroad. Rice diseases are one of the factors limiting rice production and causing significant yield reductions. Our study aims to identify the rice pathogens present in three region of Madagascar: two of these regions (Analamanga and Vakinankaratra) are located in upland region when the last (Atsinanana) is located in coastal regions. Fifty five (55) rice samples were collected and cultured on standard media. A survey questionnaire was also conducted with the farmers in order to collect information about the context in which the diseases appeared. Micro-organisms isolated were identified by morphological characteristics for fungi, gram stain and anaerobic growth test for bacteria. In addition, molecular DNA characterization was performed by PCR using universal primers for both fungi and bacteria. The amplicons obtained were sequenced and analyzed by BLAST. In Analamanga and Vakinankaratra, Alternaria sp. and Xanthomonas oryzae pv. oryzae were pre-dominant. In the Atsinanana region, however, Curvularia lunata and Pseudomonas fuscovaginae were the most present. The weather in upland regions is indeed warm and humid in summer, dry and cold in winter which favours Xanthomonas oryzae pv. oryzae and Alternaria sp.growth. Moreover, irrigation is practiced in those regions which can explain the spread of the diseases. The weather in coastal region is warm and humid all year long which tend to favor weed development all year, serving as alternative hosts for Pseudomonas fuscovaginae and Curvularia lunata in interseason. [less ▲]

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See detailSurvey of rice diseases in three regions in Madagascar
Razanakoto Mamiharisoa, Lea; De Clerck, Caroline ULg; Zalmine, F. et al

Poster (2013, February 08)

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